If this video did not help then you can also try iMyFone Fixppo - iOS System Recovery with no data loss:
Step 2: Press the sleep/wake button and lock your iPhone. Step 3: Use a microfiber cloth, and gently wipe across your screen. Step 4: If the particles do not seem to go, use a soft lint-free cloth
Restart your iPhone or iPad. Make sure that your screen is clean and free of any debris or water. Disconnect any Lightning or USB-C accessories. If your screen works after removing an accessory, try using a different outlet, cable, or charger. Remove any cases or screen protectors. The screen does not display anything. Now, if I connect to iTunes - it asks for iCloud (as if new phone, just like when the screen was working moments ago). Meaning, the phone itself is working - highly likely that the pins are damaged as I was bending that back into place (and I assume since it's experienced water, they're weak).Steps guidelines: Go to the āSetting appā option. Select āGeneralā tab and select āSoftware Updateā option there. In the manual guidelines your device will ask a āPasscodeā so enter your passcode and enter. Now you will again see option āReset All Settingā select this option and your iPhone start resetting. 4.
muS3mE.